DE3031731A1 - GAS DOSER - Google Patents

Description

DR.-ING. WALTER ABITZ DR. DIETER F. MORF DIPL.-PHYS. M. GRITSCHNEDER Patent attorneys

AUGUST 22, 1980

Postal address PO Box 86O1O9. 8OOO Munich 86

Pienzenauerstraüe 28 Telephone 98 32 22

Telegrams: Chemindus Munich Telex: (O} 5 23992

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E. I. DU PONT DE NEMORS AND COMPANY 10th and Market Streets, Wilmington, Del. 19898, V.St.A.

Gas dosimeter

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The invention relates to a dosimeter to be carried or handled by people for the detection of gaseous Impurities in the atmosphere. In particular, the invention relates to a self-contained Dosimeter that is able to measure the amount of a to integrate gaseous contamination or to determine overall.

The growing concern devoted to the health of workers exposed to air pollution in the workplace monitoring of the concentration of these atmospheric pollutants is necessary made. One development aimed at this has been based on the use of a relatively large air pump, which presses the air to be examined through a filter which traps particulate contaminants. This method is of course not suitable for the determination of gaseous impurities and allows even in the case of particles no precise determination of the particle concentration in the air sample.

Personal sampling devices, which are carried by the individual employees and pass the impurities catch have also already been used. A device that dissolves the sample using molecular diffusion of the gas to be determined is, for example, in the American Industrial Hygiene Association Journal, Volume 34, (1973), pages 78 to 81. However, this device requires the collection medium to be removed

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and careful treatment of the medium with reagents, which are precisely dosed for each analysis have to.

The disassembly of the device and the use of difficult-to-use reagents, which for each Analysis are necessary, are disadvantageous.

There is therefore still a need for a personal gas pollution dosimeter for gaseous ones Impurities, which indicates the concentration of the gas impurity over a given period of time and with the help of this a simple analysis without removing the gas collecting medium or laborious addition of others Elements or reagents is possible. ■ _-

The invention provides a personal dosimeter for determining the average concentration of a gaseous Contamination created during a given period of time, which includes:

a) a sealed or closed, bag-like or sack-like container made of a flexible polymer Material that separates a reaction chamber designed to receive a gas collection medium and at least one has sealed and adapted to receive a test reagent compartment, the seals each Compartment can be broken open individually so that the reagents are released separately into the reaction chamber can.

b) a gas diffusion device operating in a restriction the container is sealed and the only connection between the atmosphere and the interior of the

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action chamber forms.
A brief explanation of the accompanying drawings follows.

1 shows, on an enlarged scale, a perspective view of a gas diffusion device according to the invention;

Figure 2 is a top plan view of a gas pollution dosimeter with the diffusion device according to FIG. 1;

Fig. 3 is a partial view in perspective of the dosimeter of Fig. 2;

Fig. 4 is a perspective view of a gas contaminant meter using a membrane as a gas diffusion device.

The dosimeters according to the invention collect a gaseous Contamination in relation to its average concentration in the atmosphere during the collection period and allow a practical determination of this concentration. This is achieved through passive sampling the gaseous pollution in the surrounding air in relation to its concentration in this by one diffuses the contaminant into an internal part of the dosimeter in which it is held until it is analyzed. The dosimeter also contains specific color-forming reagents that are used within the dosimeter in measured quantities are sealed separately, but can be brought into contact with the collecting medium.

The collection medium that is present in a measured amount keeps the gaseous impurity or its ions in a form that is easier to analyze than the gaseous

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shaped shape. Once collected, the medium is treated with the appropriate reagents to produce color, the intensity of which depends on the amount of gaseous contamination collected. The ambient concentration in Their time average can then, as will be explained below, with a previously calibrated colorimeter or spectrophotometer.

In general, the collection medium is a material that absorbs the gaseous contaminant to be measured, adsorbs, reacts with it or combines with it in some other way. Regardless of the way in which the medium interacts with the impurity in the aforementioned manner, the amount should be or strength of the collecting medium in the dosimeter be sufficient, fully interacting with the total amount of -gaseous Impurity that is to be collected. The collection medium is often specific to the particular one to be determined gaseous contamination. Examples which are given below to illustrate, but not limit are to be interpreted, are aqueous solutions of oxidizing agents or triethanolamine for the absorption of Nitrogen dioxide, solutions of potassium or sodium tetrachloride to absorb sulfur dioxide, and solutions of sulfuric and other acids to absorb ammonia. Charcoal or powdered carbon High surface area, metal powders or metal salts or films can be used to create many organic Adsorb impurities.

Methods for colorimetric analysis for example for Sulfur dioxide, nitrogen dioxide, and ammonia in air are in the National Institute for Occupational Safety and Health under method no. 160 (publication 121, 1975), 108 (publication 136, 1974), and 205 (publication

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121, 1975). The methods described in these are easily adaptable to absorb solutions and color-forming reagents for use in the dosimeter of the invention.

An embodiment of the invention is shown in Figs. 2 and 3 / which, as described, can be shaped as follows. A base sheet 7 made of impermeable polymeric material, which is preferably flexible, is provided with at least one recess 6. Usually there are several depressions 6 available, which can be provided linearly and at intervals from one another along a circumference of the film 7, as shown. The film is preferably transparent and thermoplastic and can be made from polymers of olefin, halogenated polymers, polyester or ionomer resins. Preferred materials are shown in U.S. Patent 3,264,272 dated 2.8.1966. They are the ion copolymers of alpha-olefins and alpha-, beta-ethylenic unsaturated carboxylic acids of 3-8 carbon atoms, with 10-90% of the carboxylic acid groups being neutralized with metal ions are.

The size of the film 7 is not critical; preferably the size is such that the slide is easy to read in a dosimeter is to be used, which can be carried or transported in a simple manner by one person. The depressions 6 can easily be done by applying pressure to the film 7 with a suitable, optionally heated stamp or generated in any other way.

Pre-measured quantities of reagents are introduced into the wells 6 in any convenient manner. That Collection medium is placed in the central part of the slide. If the collection medium is a liquid, its addition can be can be done more easily by first

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In a telling manner, as in the production of the recesses 6, a recess is created in the central part of the film. These central recess is usually larger than each of the recesses 6.

After the reagent and the collecting medium have been applied to the foil 7, a second foil, i.e. cover foil 8, is used the film 7 corresponds in terms of composition and essentially in terms of size to which Slide 7 placed.

Then heat and pressure are applied to the areas 4, which the surround the wells 6 containing the reagents, for example with the aid of a conventional heat sealing die applied, creating separate compartments or chambers for each reagent. The seals or seals along the areas 4 are through careful regulation of the heat supply or by generating one only narrow seal deliberately designed to be breakable. The formation of the seals can in particular be regulated in such a way that that one obtains seals, which later by applying pressure to the reagents located in the compartments can be broken open. Optionally, adhesives or other forms of bonding can be used, provided that Breakable bonds are created in these areas. Then heat and pressure are applied to the three areas 3 exercised so that a permanent, fluid-tight bond on the three corresponding edges of the foils 7 and 8 is created will.

An elongated gas diffusion device 1 with a plurality of continuous channels 2 is parallel and in the Arranged near the fourth, non-connected edge of the base film and not parallel and flush with the fourth connected edge of the cover sheet 8. The open channels 2

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the diffusion device 1 are therefore referring to the plane of the film 7 is directed horizontally and perpendicular to the fourth edges of the films 7 and 8. The diffusion device 1 / which is sandwiched between the films 7 and 8 is inserted, is with the foils by applying heat and pressure or by means of adhesives, which for the collection medium and reagents should be impermeable and chemically inert to these components, tied together.

The bond between the diffusion device 1 and each the foils 7 and 8 should be liquid-tight and airtight, thereby completing the formation of the reaction chamber 5 will. The reaction chamber 5 is the interior of the sealed container, which is between the foils 7 and 8 is formed and contains the collection medium. The relative positions of the diffusion device 1 and the foils 7 and 8 are such that channels 2 are the only connection between the atmosphere and the interior of the Form reaction chamber 5.

The dosimeter according to FIGS. 2 and 3 can also be manufactured in the manner that the addition of the reagents and the collection medium is made last. In this case it will the dosimeter is otherwise generated in the manner described. The reagents and the collection medium can thereby be in place and put in place that the cover sheet 8 in a suitable place with a hypodermic needle pierced and a measured amount of the collection medium or reagent in the appropriate chamber or compartment injects. The holes created with the hypodermic needle can then be thermally sealed.

The diffusion device 1 allows the gaseous contamination to see ^{through each of the channels 2 after the fuck 1}

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Diffuse law, which can be expressed as follows can:

M = D. C. t A / L
whereby

M = transferred amount of gaseous impurity (mg)

D = diffusion coefficient of the gaseous impurities

2 cleaning by air (cm / min)

C = concentration of the impurity in the atmosphere (mg / cm)
t = exposure time (min.) A = cross-sectional area of the channel (cm) L = distance in the diffusion direction, the length of the channel (cm)

The values of D for various gaseous impurities can be found in the literature. The purely diffusional one Mode of transmission of the gaseous contamination through the channels at a rate in a linear relationship to their atmospheric concentration gives the integrating character of the dosimeter.

The gas diffusion device 1 is preferably made of materials that are non-hygroscopic and both is chemically and physically inert to the gaseous contamination and the collection medium. Examples are polyethylene, polypropylene, polymers or copolymers of tetrafluoroethylene and hexafluoropropylene and stainless Stole. The aforementioned polymers are preferred because they can be easily injection molded.

As can be seen from the Fick ¹ law, the influence

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The number and diameter of the channels determine the amount of gaseous pollution collected, as they are the total cross-sectional area affect which is available for transmission. The amount of contamination collected is also inversely proportional to the length of the channels. Although these parameters are not necessarily critical to the process of integration of the diffusion process found that the use of about 5-500 channels, preferably 10-100 channels, each with a diameter of about 50-1000 microns and a length of about 1.0 to 25.0 mm, preferably 3.0 to 8.0 mm, a device results that are sufficiently sensitive to low levels of environmental contaminants is, however, still of a conveniently small size.

Optionally, a porous hydrophobic film 15-1000 microns thick can be placed over the channel openings on the Inside 11 of the diffusion device 1, the side that is in communication with the inside of the reaction chamber 5, to be brought. The film can for example be made from polymers or copolymers of tetrafluoroethylene and hexafluoropropylene. The function of the film is to prevent the absorbent solution from getting in this form of collecting medium is used, flows into the channels of the diffusion device 1. The porosity of the Film and the size of its pores should therefore be chosen so that this function is obtained without the transition of the gaseous contaminant from the inner ends of the channels to the absorbent solution. This means that the diffusion of gaseous impurities through this film can be significantly greater is said to be the diffusion through the channels, so that the overall diffusion rate is essentially regulated by the channels alone. It was found that a Foil that is 50-80% porous with a pore size of 0.1 to

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3.0 microns is sufficient for this purpose if the Channels can be used in the manner described above.

Other gas diffusion devices used in the present invention Dosimeters are gas-permeable, liquid-impermeable membranes, through which the gaseous impurity can diffuse. Any of the conventional known membranes are for suitable for the intended purpose with the proviso that the membrane is chosen so that the rate of diffusion The gaseous pollution due to this varies linearly with the atmospheric concentration of the pollution varied by a wide range of such concentrations. This ensures that a dosimeter, the one using such a membrane effectively integrated. For example, if a membrane has a gas volume at high atmospheric Passes through concentrations that are disproportionate to the amount that pass through at lower concentrations, the correlation between the final amount collected and the average concentration in the Atmosphere disturbed. The membranes are typically about 10-300 microns thick and can, for example made of silicone rubber, polytetrafluoroethylene or copolymers of silicone and polycarbonate.

A dosimeter according to the invention, in which such a membrane is used as the gas diffusion device, is shown in FIG. The design and description of this dosimeter are basically the same as for the dosimeter 2 and 3, but with the following changes. In addition to the sealing of the film 7 and 8 along the Areas 3 as in Figures 2 and 3, the foils 7 and 8 of this dosimeter are also on in a similar manner the fourth side 3a sealed, whereby the formation of the

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Reaction chamber 5 is completed.

The cover sheet 8, which forms a delimitation of the reaction chamber 5, is provided with a rectangular opening, on which a correspondingly shaped membrane 10 of the type described above lies. A fastener 9, which has the shape of the outline of a rectangle, rests on the membrane 10 so that the rectangular shaped opening through the fastening element 9 exposes the membrane 10 to the atmosphere. The fastener 9 is made of the same material as the film 8 and can be used with this in a fluid-tight manner be bonded by heat and pressure. The membrane 10 is sealed in this way with the cover sheet 8 and forms the only connection between the atmosphere and the interior of the reaction chamber 5.

In addition to the gas diffusion devices described above are other devices that can be used with the dosimeter according to the invention, from the Kind of in that they diffuse or permeate the gaseous impurity through them at a rate which varies linearly with the atmospheric concentration of the pollution. For example hollow fibers of the type described in U.S. Patent Application Ser.No. 922.546 of 7/7/1978 are described, be used.

With the exception of the installation of a diffusion device the container of the dosimeter according to the invention is essentially similar to the test pack described in US Pat 3,476,515 is shown. Reference is made to this patent specification in this context.

In use, the dosimeter is exposed to the air containing the gaseous contaminant for a period of time

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exposed for which the average impurity concentration is searched. After this process, the selected reagent compartments that are used for Analysis contains necessary reagents, broken down their Content released into the reaction card and with the Collection medium mixed in this. The compartment can be broken open in a very simple manner by applying pressure to this happen, for example by squeezing with your fingers. Leave the reagents and collection medium mix thoroughly by exerting a slight pulsating pressure with the fingers on the flexible foils forming the reaction chamber.

Since the dosimeter is flexible and transparent, the contents of the reaction chamber can be viewed directly without taking a sample can be analyzed from the dosimeter. If the analysis is photometric is to be made, the dosimeter can be clamped in a position in which an electromagnetic Radiation can be directed through the contents of the reaction chamber, the unabsorbed (i.e. transmitted) radiation is directed to a suitable detector. The preferred method is to use of reagents which change the color of the collection medium depending on the amount of gaseous contaminant collected and then analyzing with visible light radiation using a colorimeter or spectrophotometer.

The dosimeter according to the invention can be calibrated so that a direct relationship between colorimetric or spectrophotometric readings and the average ambient concentration of the gaseous contaminant will. This can be accomplished through the use of a calibration procedure similar to that described in the US patent application Ser.No. 922 546 of 07/07/1978 is described.

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One such procedure involves using multiple dosimeters different known concentrations of an impurity for which the Calibration is sought, suspended. The dosimeters contain the same types and amounts of collection media and reagents. For example, spectrophotometric readings are taken for at least 2 dosimeters for each of several known concentrations are determined and a straight line is plotted using an analysis of the smallest Squares through the measurement points obtained in this way.

End of description.

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Claims (10)

Expectations ; 1.) Personal dosimeter for measuring the average concentration of a gaseous impurity over a given period of time, indicated by a bag-like or sack-like container made of polymer material with at least one compartment, which is less than occupies the entire volume of the container and leaves a reaction chamber (5), the compartment is adapted to contain a predetermined amount of a color-forming reagent and this reagent into the reaction chamber regardless of any other reagents contained in any others Compartments are present to release, and wherein the reaction chamber is designed to be a collection medium for containing the gaseous impurity, and a gas diffusion device (1) which has a plurality of continuous channels (2), which is sealed in a delimitation of the container, which channels of the diffusion device are the only connection between the atmosphere and the interior of the Form reaction chamber. - 1 - 13001 1/0747 FF 6097-C 2 2. Dosimeter according to claim l, characterized in that 5 to 500 channels are provided, each of which has a diameter of 50 to 1000 microns and a length of 1.0 to 25.5 mm. Personal dosimeter for measuring the average concentration of a gaseous pollution over a given period of time, characterized by a bag-like or sack-like container made of polymer Material with at least one compartment which takes up less than the entire volume of the container and leaves a reaction chamber (5), the compartment being adapted to hold a predetermined amount of a to contain color-forming reagent and this reagent in the reaction chamber independently of any other reagents present in any other compartments, and the reaction chamber is configured to contain a collection medium for the gaseous contaminant, and a gas diffusion device (1) in the form of a membrane, through which the gaseous contaminant passes at a rate that is in a linear relationship its concentration in the atmosphere indicates which membrane is in a limitation of the container mentioned is sealed and forms the only connection between the atmosphere and the interior of the reaction chamber. 4. Dosimeter according to claim 3, characterized in that the membrane is made of silicone rubber, polytetrafluoroethylene or copolymers of silicone and polycarbonate is. - 0 - 130011/0747 FF 6097-C, 5. Dosimeter according to claims 1, 2, 3 or 4, characterized characterized in that it contains a collection medium in the form of an absorbent solution. 6. Dosimeter according to claim 5, characterized in that the absorbing solution for sulfur dioxide, nitrogen dioxide or ammonia. 7. Dosimeter according to claim 6, characterized in that it contains at least one farbbilde.nd.es reagent. 8. Dosimeter according to claim 7, characterized in that the absorbent solution is a solution of sodium tetrachloride or potassium tetrachloride in water and the reagent is used to determine the presence of sulfur dioxide. 9. Dosimeter according to claim 7, characterized in that the absorbing solution is a solution of triethanolamine is in water and the reagent is used to determine the presence of nitrogen dioxide. 10. Dosimeter according to claim 7, characterized in that the absorbing solution is a solution of sulfuric acid is in water and the reagent is used to determine the presence of ammonia. 130011/0747